Bad stator - did it wear out or did I fry it?

[swire]

I just finished a complete rebuild of my boat and had it out several times with no problem. Last week I connected my house battery to my starting battery with a VSR. The stator on the motor is rated at 16 amps. The amp for stereo requires a 60 amp breaker. With the VSR the strong draw of the house battery is now indirectly connected to the output of the stator. The VSR was not activating when I thought it should, the voltage shown on my fish finder was 13.9 instead of 14.5, then the fish finder display started flickering so bad it is unreadable, the motor would take a lot of cranking to start, and then the next time out on the lake the boat would no longer start. After doing some diagnostics I decided to replace the stator and the motor started right up.

The motor is a 1998 90 HP Force by Mercury. The starter went bad last year and had to be replaced. A stator is similar type of technology as a starter so maybe it was wore out to. No hour meter on the motor so I have no idea on that. The motor looks good and runs good.

So my question is for anyone with a small amp stator, VSR, and heavy draw on a house battery. Was my stator wearing out and just happened to coincide with me connecting the VSR, did the extra electronics push the limits of the old stator that was wearing out, or do I simply just have too much load and will continue to fry stators? I really do not want to get stuck out on the lake again.

 

[dingbat]

Re: Bad stator - did it wear out or did I fry it?

Stators don't wear out. The stator is protected from the load by the switch box. Did you replace the switch box when you replaced the stator went last time?

Since one componet depends on the other for proper operation, ideally you should replace the stator and switch box as a pair

 

[wingless]

Re: Bad stator - did it wear out or did I fry it?

The starter and the stator would also be degraded by abnormal exposure to salt water.

Were those components exposed to excessive salt water?

 

[swire]

Re: Bad stator - did it wear out or did I fry it?

I haven't replaced the switch box, just the stator. By switch box I'm assuming you mean the rectifier? One test that I on the old stator was a resistance test. It should have been in the range of 400 to 600 ohms but mine measure around 400,000 ohms. The new one measured 680. Any idea what would cause the resistance to jump that much?

As far as I know the motor has never seen salt water. I'm not the original owner of the motor so I don't know what it saw the first 5 years of its life. I don't notice any rusting or etching that would suggest salt water.

 

[dingbat]

Re: Bad stator - did it wear out or did I fry it?

The switch box and the rectifier are two entirely different things. The switch boxes control the electronics on the motor. The rectifier is a DC bridge (a bunch of diodes) whose sole purpose is to covert the AC output of the stator into useable DC current.

Saltwater should not bother a stator. The windings, etc. are potted in epoxy.

The jump in resistance jump is typical of a break / damage in the windings. Did you notice any damage to the stator? Typically they’ll melt the epoxy or turn dark in the damaged area.

 

[swire]

Re: Bad stator - did it wear out or did I fry it?

The stator looked good. I heard that they melt or ooz out a dark substance but I didn't see anything like that. The only damage appeared to be surface damage where a plate on the motor was rubbing on the underside of one of the windings. I couldn't tell for sure but it didn't look like it wore through the outside coating. That part that was rubbing was dark but it was rubbing on the black motor. The other parts of that winding looked fine. All the magnets on the flywheel were there and in good shape. Other than the spot that was rubbed everything looked clean.

I'm not familiar with any switch box on the motor. There is a trigger assembly. That is the only other box or device other than the starter and stater solenoid. This site has a diagram of the ignition system. http://www.crowleymarine.com/mercury-outboard/parts/2530_2.cfm

 

[dingbat]

Re: Bad stator - did it wear out or did I fry it?

It looks like they got rid of the switch boxes in 1995 and intergrated some of the functions into the CDM assembles.

I would very suspect of the REG KIT-VOLT-BULL assembly. I looked for a schematic to check the functionality of this box but can't find one.

 

[swire]

Re: Bad stator - did it wear out or did I fry it?

The only diagnostic that I had come across was when troubleshooting the no spark situation. One step was to unplug the yellow wires from the stator to the rectifier. If it starts then the rectifier is bad. I haven't seen anything else related to that box.

From what I've been reading it sounds like a high demand put on the stator is one way to fry them. Since I had recently installed the VSR and was running down the lake with the radio cranked up, I'm guessing the draw of the amplifier was just too much for the stator. I'm thinking I should either remove the VSR or not play the radio while cruising down the lake. Neither are ideal but would probably save me from being stranded again. Then this fall I will look for a bigger motor with a much bigger stator.